Final answer:
According to Ohm's law, the voltage drop across a resistor is calculated with V = IR. For a balanced three-phase system, each phase has its own voltage drop, and the sum equals the source voltage.
Step-by-step explanation:
According to Ohm's law, the voltage drop, V, across a resistor when a current flows through it is calculated using the equation V = IR, where I equals the current in amps (A) and R is the resistance in ohms (Ω). This is a simplification, as the formula for three-phase systems will be different, but foundational principles from Ohm's law still apply.
For three-phase systems, each phase would have its own voltage drop calculated in this way, assuming the system is balanced. In real-world applications, additional factors such as phase angles and power factor may also need to be considered for precise calculations.
The sum of voltage drops in a closed circuit equals the source voltage, which indicates that the energy (voltage) supplied by the source is being used (dropped) across the resistances in the circuit.